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+      #
+      #
       # Copyright (C) 2006, 2007, 2008, 2009, 2010 Google Inc.
+      #
       # This program is free software; you can redistribute it and/or modify
       # it under the terms of the GNU General Public License as published by
       # the Free Software Foundation; either version 2 of the License, or
       # (at your option) any later version.
+      #
       # This program is distributed in the hope that it will be useful, but
       # WITHOUT ANY WARRANTY; without even the implied warranty of
       # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
       # General Public License for more details.
+      #
       # You should have received a copy of the GNU General Public License
       # along with this program; if not, write to the Free Software
       # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
       # 02110-1301, USA.
       """Module implementing the job queue handling.
       Locking: there's a single, large lock in the L{JobQueue} class. It's
       used by all other classes in this module.
       @var JOBQUEUE_THREADS: the number of worker threads we start for
           processing jobs
       """
       import os
       import logging
       import errno
       import re
       import time
       import weakref
       try:
         # pylint: disable-msg=E0611
         from pyinotify import pyinotify
       except ImportError:
         import pyinotify
       from ganeti import asyncnotifier
       from ganeti import constants
       from ganeti import serializer
       from ganeti import workerpool
       from ganeti import locking
       from ganeti import opcodes
       from ganeti import errors
       from ganeti import mcpu
       from ganeti import utils
       from ganeti import jstore
       from ganeti import rpc
       from ganeti import runtime
       from ganeti import netutils
       from ganeti import compat
       JOBQUEUE_THREADS = 25
       JOBS_PER_ARCHIVE_DIRECTORY = 10000
       # member lock names to be passed to @ssynchronized decorator
       _LOCK = "_lock"
       _QUEUE = "_queue"
       class CancelJob(Exception):
         """Special exception to cancel a job.
         """
       def TimeStampNow():
         """Returns the current timestamp.
         @rtype: tuple
         @return: the current time in the (seconds, microseconds) format
         """
         return utils.SplitTime(time.time())
       class _QueuedOpCode(object):
         """Encapsulates an opcode object.
         @ivar log: holds the execution log and consists of tuples
         of the form C{(log_serial, timestamp, level, message)}
         @ivar input: the OpCode we encapsulate
         @ivar status: the current status
         @ivar result: the result of the LU execution
         @ivar start_timestamp: timestamp for the start of the execution
         @ivar exec_timestamp: timestamp for the actual LU Exec() function invocation
         @ivar stop_timestamp: timestamp for the end of the execution
         """
         __slots__ = ["input", "status", "result", "log", "priority",
                      "start_timestamp", "exec_timestamp", "end_timestamp",
                      "__weakref__"]
         def __init__(self, op):
           """Constructor for the _QuededOpCode.
           @type op: L{opcodes.OpCode}
           @param op: the opcode we encapsulate
           """
           self.input = op
           self.status = constants.OP_STATUS_QUEUED
           self.result = None
           self.log = []
           self.start_timestamp = None
           self.exec_timestamp = None
           self.end_timestamp = None
           # Get initial priority (it might change during the lifetime of this opcode)
           self.priority = getattr(op, "priority", constants.OP_PRIO_DEFAULT)
         @classmethod
         def Restore(cls, state):
           """Restore the _QueuedOpCode from the serialized form.
           @type state: dict
           @param state: the serialized state
           @rtype: _QueuedOpCode
           @return: a new _QueuedOpCode instance
           """
           obj = _QueuedOpCode.__new__(cls)
           obj.input = opcodes.OpCode.LoadOpCode(state["input"])
           obj.status = state["status"]
           obj.result = state["result"]
           obj.log = state["log"]
           obj.start_timestamp = state.get("start_timestamp", None)
           obj.exec_timestamp = state.get("exec_timestamp", None)
           obj.end_timestamp = state.get("end_timestamp", None)
           obj.priority = state.get("priority", constants.OP_PRIO_DEFAULT)
           return obj
         def Serialize(self):
           """Serializes this _QueuedOpCode.
           @rtype: dict
           @return: the dictionary holding the serialized state
           """
           return {
             "input": self.input.__getstate__(),
             "status": self.status,
             "result": self.result,
             "log": self.log,
             "start_timestamp": self.start_timestamp,
             "exec_timestamp": self.exec_timestamp,
             "end_timestamp": self.end_timestamp,
             "priority": self.priority,
+            }
       class _QueuedJob(object):
         """In-memory job representation.
         This is what we use to track the user-submitted jobs. Locking must
         be taken care of by users of this class.
         @type queue: L{JobQueue}
         @ivar queue: the parent queue
         @ivar id: the job ID
         @type ops: list
         @ivar ops: the list of _QueuedOpCode that constitute the job
         @type log_serial: int
         @ivar log_serial: holds the index for the next log entry
         @ivar received_timestamp: the timestamp for when the job was received
         @ivar start_timestmap: the timestamp for start of execution
         @ivar end_timestamp: the timestamp for end of execution
         """
         # pylint: disable-msg=W0212
         __slots__ = ["queue", "id", "ops", "log_serial", "ops_iter", "cur_opctx",
                      "received_timestamp", "start_timestamp", "end_timestamp",
                      "__weakref__"]
         def __init__(self, queue, job_id, ops):
           """Constructor for the _QueuedJob.
           @type queue: L{JobQueue}
           @param queue: our parent queue
           @type job_id: job_id
           @param job_id: our job id
           @type ops: list
           @param ops: the list of opcodes we hold, which will be encapsulated
               in _QueuedOpCodes
           """
           if not ops:
             raise errors.GenericError("A job needs at least one opcode")
           self.queue = queue
           self.id = job_id
           self.ops = [_QueuedOpCode(op) for op in ops]
           self.log_serial = 0
           self.received_timestamp = TimeStampNow()
           self.start_timestamp = None
           self.end_timestamp = None
           self._InitInMemory(self)
         @staticmethod
         def _InitInMemory(obj):
           """Initializes in-memory variables.
           """
           obj.ops_iter = None
           obj.cur_opctx = None
         def __repr__(self):
           status = ["%s.%s" % (self.__class__.__module__, self.__class__.__name__),
                     "id=%s" % self.id,
                     "ops=%s" % ",".join([op.input.Summary() for op in self.ops])]
           return "<%s at %#x>" % (" ".join(status), id(self))
         @classmethod
         def Restore(cls, queue, state):
           """Restore a _QueuedJob from serialized state:
           @type queue: L{JobQueue}
           @param queue: to which queue the restored job belongs
           @type state: dict
           @param state: the serialized state
           @rtype: _JobQueue
           @return: the restored _JobQueue instance
           """
           obj = _QueuedJob.__new__(cls)
           obj.queue = queue
           obj.id = state["id"]
           obj.received_timestamp = state.get("received_timestamp", None)
           obj.start_timestamp = state.get("start_timestamp", None)
           obj.end_timestamp = state.get("end_timestamp", None)
           obj.ops = []
           obj.log_serial = 0
           for op_state in state["ops"]:
             op = _QueuedOpCode.Restore(op_state)
             for log_entry in op.log:
               obj.log_serial = max(obj.log_serial, log_entry[0])
             obj.ops.append(op)
           cls._InitInMemory(obj)
           return obj
         def Serialize(self):
           """Serialize the _JobQueue instance.
           @rtype: dict
           @return: the serialized state
           """
           return {
             "id": self.id,
             "ops": [op.Serialize() for op in self.ops],
             "start_timestamp": self.start_timestamp,
             "end_timestamp": self.end_timestamp,
             "received_timestamp": self.received_timestamp,
+            }
         def CalcStatus(self):
           """Compute the status of this job.
           This function iterates over all the _QueuedOpCodes in the job and
           based on their status, computes the job status.
           The algorithm is:
             - if we find a cancelled, or finished with error, the job
               status will be the same
             - otherwise, the last opcode with the status one of:
                 - waitlock
                 - canceling
                 - running
               will determine the job status
             - otherwise, it means either all opcodes are queued, or success,
               and the job status will be the same
           @return: the job status
           """
           status = constants.JOB_STATUS_QUEUED
           all_success = True
           for op in self.ops:
             if op.status == constants.OP_STATUS_SUCCESS:
               continue
             all_success = False
             if op.status == constants.OP_STATUS_QUEUED:
               pass
             elif op.status == constants.OP_STATUS_WAITLOCK:
               status = constants.JOB_STATUS_WAITLOCK
             elif op.status == constants.OP_STATUS_RUNNING:
               status = constants.JOB_STATUS_RUNNING
             elif op.status == constants.OP_STATUS_CANCELING:
               status = constants.JOB_STATUS_CANCELING
               break
             elif op.status == constants.OP_STATUS_ERROR:
               status = constants.JOB_STATUS_ERROR
               # The whole job fails if one opcode failed
               break
             elif op.status == constants.OP_STATUS_CANCELED:
               status = constants.OP_STATUS_CANCELED
               break
           if all_success:
             status = constants.JOB_STATUS_SUCCESS
           return status
         def CalcPriority(self):
           """Gets the current priority for this job.
           Only unfinished opcodes are considered. When all are done, the default
           priority is used.
           @rtype: int
           """
           priorities = [op.priority for op in self.ops
                         if op.status not in constants.OPS_FINALIZED]
           if not priorities:
             # All opcodes are done, assume default priority
             return constants.OP_PRIO_DEFAULT
           return min(priorities)
         def GetLogEntries(self, newer_than):
           """Selectively returns the log entries.
           @type newer_than: None or int
           @param newer_than: if this is None, return all log entries,
               otherwise return only the log entries with serial higher
               than this value
           @rtype: list
           @return: the list of the log entries selected
           """
           if newer_than is None:
             serial = -1
           else:
             serial = newer_than
           entries = []
           for op in self.ops:
             entries.extend(filter(lambda entry: entry[0] > serial, op.log))
           return entries
         def GetInfo(self, fields):
           """Returns information about a job.
           @type fields: list
           @param fields: names of fields to return
           @rtype: list
           @return: list with one element for each field
           @raise errors.OpExecError: when an invalid field
               has been passed
           """
           row = []
           for fname in fields:
             if fname == "id":
               row.append(self.id)
             elif fname == "status":
               row.append(self.CalcStatus())
             elif fname == "priority":
               row.append(self.CalcPriority())
             elif fname == "ops":
               row.append([op.input.__getstate__() for op in self.ops])
             elif fname == "opresult":
               row.append([op.result for op in self.ops])
             elif fname == "opstatus":
               row.append([op.status for op in self.ops])
             elif fname == "oplog":
               row.append([op.log for op in self.ops])
             elif fname == "opstart":
               row.append([op.start_timestamp for op in self.ops])
             elif fname == "opexec":
               row.append([op.exec_timestamp for op in self.ops])
             elif fname == "opend":
               row.append([op.end_timestamp for op in self.ops])
             elif fname == "oppriority":
               row.append([op.priority for op in self.ops])
             elif fname == "received_ts":
               row.append(self.received_timestamp)
             elif fname == "start_ts":
               row.append(self.start_timestamp)
             elif fname == "end_ts":
               row.append(self.end_timestamp)
             elif fname == "summary":
               row.append([op.input.Summary() for op in self.ops])
             else:
               raise errors.OpExecError("Invalid self query field '%s'" % fname)
           return row
         def MarkUnfinishedOps(self, status, result):
           """Mark unfinished opcodes with a given status and result.
           This is an utility function for marking all running or waiting to
           be run opcodes with a given status. Opcodes which are already
           finalised are not changed.
           @param status: a given opcode status
           @param result: the opcode result
           """
           not_marked = True
           for op in self.ops:
             if op.status in constants.OPS_FINALIZED:
               assert not_marked, "Finalized opcodes found after non-finalized ones"
               continue
             op.status = status
             op.result = result
             not_marked = False
         def Cancel(self):
           """Marks job as canceled/-ing if possible.
           @rtype: tuple; (bool, string)
           @return: Boolean describing whether job was successfully canceled or marked
             as canceling and a text message
           """
           status = self.CalcStatus()
           if status == constants.JOB_STATUS_QUEUED:
             self.MarkUnfinishedOps(constants.OP_STATUS_CANCELED,
                                    "Job canceled by request")
             return (True, "Job %s canceled" % self.id)
           elif status == constants.JOB_STATUS_WAITLOCK:
             # The worker will notice the new status and cancel the job
             self.MarkUnfinishedOps(constants.OP_STATUS_CANCELING, None)
             return (True, "Job %s will be canceled" % self.id)
           else:
             logging.debug("Job %s is no longer waiting in the queue", self.id)
             return (False, "Job %s is no longer waiting in the queue" % self.id)
       class _OpExecCallbacks(mcpu.OpExecCbBase):
         def __init__(self, queue, job, op):
           """Initializes this class.
           @type queue: L{JobQueue}
           @param queue: Job queue
           @type job: L{_QueuedJob}
           @param job: Job object
           @type op: L{_QueuedOpCode}
           @param op: OpCode
           """
           assert queue, "Queue is missing"
           assert job, "Job is missing"
           assert op, "Opcode is missing"
           self._queue = queue
           self._job = job
           self._op = op
         def _CheckCancel(self):
           """Raises an exception to cancel the job if asked to.
           """
           # Cancel here if we were asked to
           if self._op.status == constants.OP_STATUS_CANCELING:
             logging.debug("Canceling opcode")
             raise CancelJob()
         @locking.ssynchronized(_QUEUE, shared=1)
         def NotifyStart(self):
           """Mark the opcode as running, not lock-waiting.
           This is called from the mcpu code as a notifier function, when the LU is
           finally about to start the Exec() method. Of course, to have end-user
           visible results, the opcode must be initially (before calling into
           Processor.ExecOpCode) set to OP_STATUS_WAITLOCK.
           """
           assert self._op in self._job.ops
           assert self._op.status in (constants.OP_STATUS_WAITLOCK,
                                      constants.OP_STATUS_CANCELING)
           # Cancel here if we were asked to
           self._CheckCancel()
           logging.debug("Opcode is now running")
           self._op.status = constants.OP_STATUS_RUNNING
           self._op.exec_timestamp = TimeStampNow()
           # And finally replicate the job status
           self._queue.UpdateJobUnlocked(self._job)
         @locking.ssynchronized(_QUEUE, shared=1)
         def _AppendFeedback(self, timestamp, log_type, log_msg):
           """Internal feedback append function, with locks
           """
           self._job.log_serial += 1
           self._op.log.append((self._job.log_serial, timestamp, log_type, log_msg))
           self._queue.UpdateJobUnlocked(self._job, replicate=False)
         def Feedback(self, *args):
           """Append a log entry.
           """
           assert len(args) < 3
           if len(args) == 1:
             log_type = constants.ELOG_MESSAGE
             log_msg = args[0]
           else:
             (log_type, log_msg) = args
           # The time is split to make serialization easier and not lose
           # precision.
           timestamp = utils.SplitTime(time.time())
           self._AppendFeedback(timestamp, log_type, log_msg)
         def CheckCancel(self):
           """Check whether job has been cancelled.
           """
           assert self._op.status in (constants.OP_STATUS_WAITLOCK,
                                      constants.OP_STATUS_CANCELING)
           # Cancel here if we were asked to
           self._CheckCancel()
       class _JobChangesChecker(object):
         def __init__(self, fields, prev_job_info, prev_log_serial):
           """Initializes this class.
           @type fields: list of strings
           @param fields: Fields requested by LUXI client
           @type prev_job_info: string
           @param prev_job_info: previous job info, as passed by the LUXI client
           @type prev_log_serial: string
           @param prev_log_serial: previous job serial, as passed by the LUXI client
           """
           self._fields = fields
           self._prev_job_info = prev_job_info
           self._prev_log_serial = prev_log_serial
         def __call__(self, job):
           """Checks whether job has changed.
           @type job: L{_QueuedJob}
           @param job: Job object
           """
           status = job.CalcStatus()
           job_info = job.GetInfo(self._fields)
           log_entries = job.GetLogEntries(self._prev_log_serial)
           # Serializing and deserializing data can cause type changes (e.g. from
           # tuple to list) or precision loss. We're doing it here so that we get
           # the same modifications as the data received from the client. Without
           # this, the comparison afterwards might fail without the data being
           # significantly different.
           # TODO: we just deserialized from disk, investigate how to make sure that
           # the job info and log entries are compatible to avoid this further step.
           # TODO: Doing something like in testutils.py:UnifyValueType might be more
           # efficient, though floats will be tricky
           job_info = serializer.LoadJson(serializer.DumpJson(job_info))
           log_entries = serializer.LoadJson(serializer.DumpJson(log_entries))
           # Don't even try to wait if the job is no longer running, there will be
           # no changes.
           if (status not in (constants.JOB_STATUS_QUEUED,
                              constants.JOB_STATUS_RUNNING,
                              constants.JOB_STATUS_WAITLOCK) or
               job_info != self._prev_job_info or
               (log_entries and self._prev_log_serial != log_entries[0][0])):
             logging.debug("Job %s changed", job.id)
             return (job_info, log_entries)
           return None
       class _JobFileChangesWaiter(object):
         def __init__(self, filename):
           """Initializes this class.
           @type filename: string
           @param filename: Path to job file
           @raises errors.InotifyError: if the notifier cannot be setup
           """
           self._wm = pyinotify.WatchManager()
           self._inotify_handler = \
             asyncnotifier.SingleFileEventHandler(self._wm, self._OnInotify, filename)
           self._notifier = \
             pyinotify.Notifier(self._wm, default_proc_fun=self._inotify_handler)
           try:
             self._inotify_handler.enable()
           except Exception:
             # pyinotify doesn't close file descriptors automatically
             self._notifier.stop()
             raise
         def _OnInotify(self, notifier_enabled):
           """Callback for inotify.
           """
           if not notifier_enabled:
             self._inotify_handler.enable()
         def Wait(self, timeout):
           """Waits for the job file to change.
           @type timeout: float
           @param timeout: Timeout in seconds
           @return: Whether there have been events
           """
           assert timeout >= 0
           have_events = self._notifier.check_events(timeout * 1000)
           if have_events:
             self._notifier.read_events()
           self._notifier.process_events()
           return have_events
         def Close(self):
           """Closes underlying notifier and its file descriptor.
           """
           self._notifier.stop()
       class _JobChangesWaiter(object):
         def __init__(self, filename):
           """Initializes this class.
           @type filename: string
           @param filename: Path to job file
           """
           self._filewaiter = None
           self._filename = filename
         def Wait(self, timeout):
           """Waits for a job to change.
           @type timeout: float
           @param timeout: Timeout in seconds
           @return: Whether there have been events
           """
           if self._filewaiter:
             return self._filewaiter.Wait(timeout)
           # Lazy setup: Avoid inotify setup cost when job file has already changed.
           # If this point is reached, return immediately and let caller check the job
           # file again in case there were changes since the last check. This avoids a
           # race condition.
           self._filewaiter = _JobFileChangesWaiter(self._filename)
           return True
         def Close(self):
           """Closes underlying waiter.
           """
           if self._filewaiter:
             self._filewaiter.Close()
       class _WaitForJobChangesHelper(object):
         """Helper class using inotify to wait for changes in a job file.
         This class takes a previous job status and serial, and alerts the client when
         the current job status has changed.
         """
         @staticmethod
         def _CheckForChanges(job_load_fn, check_fn):
           job = job_load_fn()
           if not job:
             raise errors.JobLost()
           result = check_fn(job)
           if result is None:
             raise utils.RetryAgain()
           return result
         def __call__(self, filename, job_load_fn,
                      fields, prev_job_info, prev_log_serial, timeout):
           """Waits for changes on a job.
           @type filename: string
           @param filename: File on which to wait for changes
           @type job_load_fn: callable
           @param job_load_fn: Function to load job
           @type fields: list of strings
           @param fields: Which fields to check for changes
           @type prev_job_info: list or None
           @param prev_job_info: Last job information returned
           @type prev_log_serial: int
           @param prev_log_serial: Last job message serial number
           @type timeout: float
           @param timeout: maximum time to wait in seconds
           """
           try:
             check_fn = _JobChangesChecker(fields, prev_job_info, prev_log_serial)
             waiter = _JobChangesWaiter(filename)
             try:
               return utils.Retry(compat.partial(self._CheckForChanges,
                                                 job_load_fn, check_fn),
                                  utils.RETRY_REMAINING_TIME, timeout,
                                  wait_fn=waiter.Wait)
             finally:
               waiter.Close()
           except (errors.InotifyError, errors.JobLost):
             return None
           except utils.RetryTimeout:
             return constants.JOB_NOTCHANGED
       def _EncodeOpError(err):
         """Encodes an error which occurred while processing an opcode.
         """
         if isinstance(err, errors.GenericError):
           to_encode = err
         else:
           to_encode = errors.OpExecError(str(err))
         return errors.EncodeException(to_encode)
       class _TimeoutStrategyWrapper:
         def __init__(self, fn):
           """Initializes this class.
           """
           self._fn = fn
           self._next = None
         def _Advance(self):
           """Gets the next timeout if necessary.
           """
           if self._next is None:
             self._next = self._fn()
         def Peek(self):
           """Returns the next timeout.
           """
           self._Advance()
           return self._next
         def Next(self):
           """Returns the current timeout and advances the internal state.
           """
           self._Advance()
           result = self._next
           self._next = None
           return result
       class _OpExecContext:
         def __init__(self, op, index, log_prefix, timeout_strategy_factory):
           """Initializes this class.
           """
           self.op = op
           self.index = index
           self.log_prefix = log_prefix
           self.summary = op.input.Summary()
           self._timeout_strategy_factory = timeout_strategy_factory
           self._ResetTimeoutStrategy()
         def _ResetTimeoutStrategy(self):
           """Creates a new timeout strategy.
           """
           self._timeout_strategy = \
             _TimeoutStrategyWrapper(self._timeout_strategy_factory().NextAttempt)
         def CheckPriorityIncrease(self):
           """Checks whether priority can and should be increased.
           Called when locks couldn't be acquired.
           """
           op = self.op
           # Exhausted all retries and next round should not use blocking acquire
           # for locks?
           if (self._timeout_strategy.Peek() is None and
               op.priority > constants.OP_PRIO_HIGHEST):
             logging.debug("Increasing priority")
             op.priority -= 1
             self._ResetTimeoutStrategy()
             return True
           return False
         def GetNextLockTimeout(self):
           """Returns the next lock acquire timeout.
           """
           return self._timeout_strategy.Next()
       class _JobProcessor(object):
         def __init__(self, queue, opexec_fn, job,
                      _timeout_strategy_factory=mcpu.LockAttemptTimeoutStrategy):
           """Initializes this class.
           """
           self.queue = queue
           self.opexec_fn = opexec_fn
           self.job = job
           self._timeout_strategy_factory = _timeout_strategy_factory
         @staticmethod
         def _FindNextOpcode(job, timeout_strategy_factory):
           """Locates the next opcode to run.
           @type job: L{_QueuedJob}
           @param job: Job object
           @param timeout_strategy_factory: Callable to create new timeout strategy
           """
           # Create some sort of a cache to speed up locating next opcode for future
           # lookups
           # TODO: Consider splitting _QueuedJob.ops into two separate lists, one for
           # pending and one for processed ops.
           if job.ops_iter is None:
             job.ops_iter = enumerate(job.ops)
           # Find next opcode to run
           while True:
             try:
               (idx, op) = job.ops_iter.next()
             except StopIteration:
               raise errors.ProgrammerError("Called for a finished job")
             if op.status == constants.OP_STATUS_RUNNING:
               # Found an opcode already marked as running
               raise errors.ProgrammerError("Called for job marked as running")
             opctx = _OpExecContext(op, idx, "Op %s/%s" % (idx + 1, len(job.ops)),
                                    timeout_strategy_factory)
             if op.status == constants.OP_STATUS_CANCELED:
               # Cancelled jobs are handled by the caller
               assert not compat.any(i.status != constants.OP_STATUS_CANCELED
                                     for i in job.ops[idx:])
             elif op.status in constants.OPS_FINALIZED:
               # This is a job that was partially completed before master daemon
               # shutdown, so it can be expected that some opcodes are already
               # completed successfully (if any did error out, then the whole job
               # should have been aborted and not resubmitted for processing).
               logging.info("%s: opcode %s already processed, skipping",
                            opctx.log_prefix, opctx.summary)
               continue
             return opctx
         @staticmethod
         def _MarkWaitlock(job, op):
           """Marks an opcode as waiting for locks.
           The job's start timestamp is also set if necessary.
           @type job: L{_QueuedJob}
           @param job: Job object
           @type op: L{_QueuedOpCode}
           @param op: Opcode object
           """
           assert op in job.ops
           op.status = constants.OP_STATUS_WAITLOCK
           op.result = None
           op.start_timestamp = TimeStampNow()
           if job.start_timestamp is None:
             job.start_timestamp = op.start_timestamp
         def _ExecOpCodeUnlocked(self, opctx):
           """Processes one opcode and returns the result.
           """
           op = opctx.op
           assert op.status == constants.OP_STATUS_WAITLOCK
           timeout = opctx.GetNextLockTimeout()
           try:
             # Make sure not to hold queue lock while calling ExecOpCode
             result = self.opexec_fn(op.input,
                                     _OpExecCallbacks(self.queue, self.job, op),
                                     timeout=timeout, priority=op.priority)
           except mcpu.LockAcquireTimeout:
             assert timeout is not None, "Received timeout for blocking acquire"
             logging.debug("Couldn't acquire locks in %0.6fs", timeout)
             assert op.status == constants.OP_STATUS_WAITLOCK
             return (constants.OP_STATUS_QUEUED, None)
           except CancelJob:
             logging.exception("%s: Canceling job", opctx.log_prefix)
             assert op.status == constants.OP_STATUS_CANCELING
             return (constants.OP_STATUS_CANCELING, None)
           except Exception, err: # pylint: disable-msg=W0703
             logging.exception("%s: Caught exception in %s",
                               opctx.log_prefix, opctx.summary)
             return (constants.OP_STATUS_ERROR, _EncodeOpError(err))
           else:
             logging.debug("%s: %s successful",
                           opctx.log_prefix, opctx.summary)
             return (constants.OP_STATUS_SUCCESS, result)
         def __call__(self, _nextop_fn=None):
           """Continues execution of a job.
           @param _nextop_fn: Callback function for tests
           @rtype: bool
           @return: True if job is finished, False if processor needs to be called
                    again
           """
           queue = self.queue
           job = self.job
           logging.debug("Processing job %s", job.id)
           queue.acquire(shared=1)
           try:
             opcount = len(job.ops)
             # Is a previous opcode still pending?
             if job.cur_opctx:
               opctx = job.cur_opctx
             else:
               if __debug__ and _nextop_fn:
                 _nextop_fn()
               opctx = self._FindNextOpcode(job, self._timeout_strategy_factory)
             op = opctx.op
             # Consistency check
             assert compat.all(i.status in (constants.OP_STATUS_QUEUED,
                                            constants.OP_STATUS_CANCELED)
                               for i in job.ops[opctx.index:])
             assert op.status in (constants.OP_STATUS_QUEUED,
                                  constants.OP_STATUS_WAITLOCK,
                                  constants.OP_STATUS_CANCELED)
             assert (op.priority <= constants.OP_PRIO_LOWEST and
                     op.priority >= constants.OP_PRIO_HIGHEST)
             if op.status != constants.OP_STATUS_CANCELED:
               # Prepare to start opcode
               self._MarkWaitlock(job, op)
               assert op.status == constants.OP_STATUS_WAITLOCK
               assert job.CalcStatus() == constants.JOB_STATUS_WAITLOCK
               # Write to disk
               queue.UpdateJobUnlocked(job)
               logging.info("%s: opcode %s waiting for locks",
                            opctx.log_prefix, opctx.summary)
               queue.release()
               try:
                 (op_status, op_result) = self._ExecOpCodeUnlocked(opctx)
               finally:
                 queue.acquire(shared=1)
               op.status = op_status
               op.result = op_result
               if op.status == constants.OP_STATUS_QUEUED:
                 # Couldn't get locks in time
                 assert not op.end_timestamp
               else:
                 # Finalize opcode
                 op.end_timestamp = TimeStampNow()
                 if op.status == constants.OP_STATUS_CANCELING:
                   assert not compat.any(i.status != constants.OP_STATUS_CANCELING
                                         for i in job.ops[opctx.index:])
                 else:
                   assert op.status in constants.OPS_FINALIZED
             if op.status == constants.OP_STATUS_QUEUED:
               finalize = False
               opctx.CheckPriorityIncrease()
               # Keep around for another round
               job.cur_opctx = opctx
               assert (op.priority <= constants.OP_PRIO_LOWEST and
                       op.priority >= constants.OP_PRIO_HIGHEST)
               # In no case must the status be finalized here
               assert job.CalcStatus() == constants.JOB_STATUS_QUEUED
               queue.UpdateJobUnlocked(job)
             else:
               # Ensure all opcodes so far have been successful
               assert (opctx.index == 0 or
                       compat.all(i.status == constants.OP_STATUS_SUCCESS
                                  for i in job.ops[:opctx.index]))
               # Reset context
               job.cur_opctx = None
               if op.status == constants.OP_STATUS_SUCCESS:
                 finalize = False
               elif op.status == constants.OP_STATUS_ERROR:
                 # Ensure failed opcode has an exception as its result
                 assert errors.GetEncodedError(job.ops[opctx.index].result)
                 to_encode = errors.OpExecError("Preceding opcode failed")
                 job.MarkUnfinishedOps(constants.OP_STATUS_ERROR,
                                       _EncodeOpError(to_encode))
                 finalize = True
                 # Consistency check
                 assert compat.all(i.status == constants.OP_STATUS_ERROR and
                                   errors.GetEncodedError(i.result)
                                   for i in job.ops[opctx.index:])
               elif op.status == constants.OP_STATUS_CANCELING:
                 job.MarkUnfinishedOps(constants.OP_STATUS_CANCELED,
                                       "Job canceled by request")
                 finalize = True
               elif op.status == constants.OP_STATUS_CANCELED:
                 finalize = True
               else:
                 raise errors.ProgrammerError("Unknown status '%s'" % op.status)
               # Finalizing or last opcode?
               if finalize or opctx.index == (opcount - 1):
                 # All opcodes have been run, finalize job
                 job.end_timestamp = TimeStampNow()
               # Write to disk. If the job status is final, this is the final write
               # allowed. Once the file has been written, it can be archived anytime.
               queue.UpdateJobUnlocked(job)
               if finalize or opctx.index == (opcount - 1):
                 logging.info("Finished job %s, status = %s", job.id, job.CalcStatus())
                 return True
             return False
           finally:
             queue.release()
       class _JobQueueWorker(workerpool.BaseWorker):
         """The actual job workers.
         """
         def RunTask(self, job): # pylint: disable-msg=W0221
           """Job executor.
           This functions processes a job. It is closely tied to the L{_QueuedJob} and
           L{_QueuedOpCode} classes.
           @type job: L{_QueuedJob}
           @param job: the job to be processed
           """
           queue = job.queue
           assert queue == self.pool.queue
           self.SetTaskName("Job%s" % job.id)
           proc = mcpu.Processor(queue.context, job.id)
           if not _JobProcessor(queue, proc.ExecOpCode, job)():
             # Schedule again
             raise workerpool.DeferTask(priority=job.CalcPriority())
       class _JobQueueWorkerPool(workerpool.WorkerPool):
         """Simple class implementing a job-processing workerpool.
         """
         def __init__(self, queue):
           super(_JobQueueWorkerPool, self).__init__("JobQueue",
                                                     JOBQUEUE_THREADS,
                                                     _JobQueueWorker)
           self.queue = queue
       def _RequireOpenQueue(fn):
         """Decorator for "public" functions.
         This function should be used for all 'public' functions. That is,
         functions usually called from other classes. Note that this should
         be applied only to methods (not plain functions), since it expects
         that the decorated function is called with a first argument that has
         a '_queue_filelock' argument.
         @warning: Use this decorator only after locking.ssynchronized
         Example::
           @locking.ssynchronized(_LOCK)
           @_RequireOpenQueue
           def Example(self):
             pass
         """
         def wrapper(self, *args, **kwargs):
           # pylint: disable-msg=W0212
           assert self._queue_filelock is not None, "Queue should be open"
           return fn(self, *args, **kwargs)
         return wrapper
       class JobQueue(object):
         """Queue used to manage the jobs.
         @cvar _RE_JOB_FILE: regex matching the valid job file names
         """
         _RE_JOB_FILE = re.compile(r"^job-(%s)$" % constants.JOB_ID_TEMPLATE)
         def __init__(self, context):
           """Constructor for JobQueue.
           The constructor will initialize the job queue object and then
           start loading the current jobs from disk, either for starting them
           (if they were queue) or for aborting them (if they were already
           running).
           @type context: GanetiContext
           @param context: the context object for access to the configuration
               data and other ganeti objects
           """
           self.context = context
           self._memcache = weakref.WeakValueDictionary()
           self._my_hostname = netutils.Hostname.GetSysName()
           # The Big JobQueue lock. If a code block or method acquires it in shared
           # mode safe it must guarantee concurrency with all the code acquiring it in
           # shared mode, including itself. In order not to acquire it at all
           # concurrency must be guaranteed with all code acquiring it in shared mode
           # and all code acquiring it exclusively.
           self._lock = locking.SharedLock("JobQueue")
           self.acquire = self._lock.acquire
           self.release = self._lock.release
           # Initialize the queue, and acquire the filelock.
           # This ensures no other process is working on the job queue.
           self._queue_filelock = jstore.InitAndVerifyQueue(must_lock=True)
           # Read serial file
           self._last_serial = jstore.ReadSerial()
           assert self._last_serial is not None, ("Serial file was modified between"
                                                  " check in jstore and here")
           # Get initial list of nodes
           self._nodes = dict((n.name, n.primary_ip)
                              for n in self.context.cfg.GetAllNodesInfo().values()
                              if n.master_candidate)
           # Remove master node
           self._nodes.pop(self._my_hostname, None)
           # TODO: Check consistency across nodes
           self._queue_size = 0
           self._UpdateQueueSizeUnlocked()
           self._drained = self._IsQueueMarkedDrain()
           # Setup worker pool
           self._wpool = _JobQueueWorkerPool(self)
           try:
             self._InspectQueue()
           except:
             self._wpool.TerminateWorkers()
             raise
         @locking.ssynchronized(_LOCK)
         @_RequireOpenQueue
         def _InspectQueue(self):
           """Loads the whole job queue and resumes unfinished jobs.
           This function needs the lock here because WorkerPool.AddTask() may start a
           job while we're still doing our work.
           """
           logging.info("Inspecting job queue")
           restartjobs = []
           all_job_ids = self._GetJobIDsUnlocked()
           jobs_count = len(all_job_ids)
           lastinfo = time.time()
           for idx, job_id in enumerate(all_job_ids):
             # Give an update every 1000 jobs or 10 seconds
             if (idx % 1000 == 0 or time.time() >= (lastinfo + 10.0) or
                 idx == (jobs_count - 1)):
               logging.info("Job queue inspection: %d/%d (%0.1f %%)",
                            idx, jobs_count - 1, 100.0 * (idx + 1) / jobs_count)
               lastinfo = time.time()
             job = self._LoadJobUnlocked(job_id)
             # a failure in loading the job can cause 'None' to be returned
             if job is None:
               continue
             status = job.CalcStatus()
             if status in (constants.JOB_STATUS_QUEUED, ):
               restartjobs.append(job)
             elif status in (constants.JOB_STATUS_RUNNING,
                             constants.JOB_STATUS_WAITLOCK,
                             constants.JOB_STATUS_CANCELING):
               logging.warning("Unfinished job %s found: %s", job.id, job)
               job.MarkUnfinishedOps(constants.OP_STATUS_ERROR,
                                     "Unclean master daemon shutdown")
               self.UpdateJobUnlocked(job)
           if restartjobs:
             logging.info("Restarting %s jobs", len(restartjobs))
             self._EnqueueJobs(restartjobs)
           logging.info("Job queue inspection finished")
         @locking.ssynchronized(_LOCK)
         @_RequireOpenQueue
         def AddNode(self, node):
           """Register a new node with the queue.
           @type node: L{objects.Node}
           @param node: the node object to be added
           """
           node_name = node.name
           assert node_name != self._my_hostname
           # Clean queue directory on added node
           result = rpc.RpcRunner.call_jobqueue_purge(node_name)
           msg = result.fail_msg
           if msg:
             logging.warning("Cannot cleanup queue directory on node %s: %s",
                             node_name, msg)
           if not node.master_candidate:
             # remove if existing, ignoring errors
             self._nodes.pop(node_name, None)
             # and skip the replication of the job ids
             return
           # Upload the whole queue excluding archived jobs
           files = [self._GetJobPath(job_id) for job_id in self._GetJobIDsUnlocked()]
           # Upload current serial file
           files.append(constants.JOB_QUEUE_SERIAL_FILE)
           for file_name in files:
             # Read file content
             content = utils.ReadFile(file_name)
             result = rpc.RpcRunner.call_jobqueue_update([node_name],
                                                         [node.primary_ip],
                                                         file_name, content)
             msg = result[node_name].fail_msg
             if msg:
               logging.error("Failed to upload file %s to node %s: %s",
                             file_name, node_name, msg)
           self._nodes[node_name] = node.primary_ip
         @locking.ssynchronized(_LOCK)
         @_RequireOpenQueue
         def RemoveNode(self, node_name):
           """Callback called when removing nodes from the cluster.
           @type node_name: str
           @param node_name: the name of the node to remove
           """
           self._nodes.pop(node_name, None)
         @staticmethod
         def _CheckRpcResult(result, nodes, failmsg):
           """Verifies the status of an RPC call.
           Since we aim to keep consistency should this node (the current
           master) fail, we will log errors if our rpc fail, and especially
           log the case when more than half of the nodes fails.
           @param result: the data as returned from the rpc call
           @type nodes: list
           @param nodes: the list of nodes we made the call to
           @type failmsg: str
           @param failmsg: the identifier to be used for logging
           """
           failed = []
           success = []
           for node in nodes:
             msg = result[node].fail_msg
             if msg:
               failed.append(node)
               logging.error("RPC call %s (%s) failed on node %s: %s",
                             result[node].call, failmsg, node, msg)
             else:
               success.append(node)
           # +1 for the master node
           if (len(success) + 1) < len(failed):
             # TODO: Handle failing nodes
             logging.error("More than half of the nodes failed")
         def _GetNodeIp(self):
           """Helper for returning the node name/ip list.
           @rtype: (list, list)
           @return: a tuple of two lists, the first one with the node
               names and the second one with the node addresses
           """
           # TODO: Change to "tuple(map(list, zip(*self._nodes.items())))"?
           name_list = self._nodes.keys()
           addr_list = [self._nodes[name] for name in name_list]
           return name_list, addr_list
         def _UpdateJobQueueFile(self, file_name, data, replicate):
           """Writes a file locally and then replicates it to all nodes.
           This function will replace the contents of a file on the local
           node and then replicate it to all the other nodes we have.
           @type file_name: str
           @param file_name: the path of the file to be replicated
           @type data: str
           @param data: the new contents of the file
           @type replicate: boolean
           @param replicate: whether to spread the changes to the remote nodes
           """
           getents = runtime.GetEnts()
           utils.WriteFile(file_name, data=data, uid=getents.masterd_uid,
                           gid=getents.masterd_gid)
           if replicate:
             names, addrs = self._GetNodeIp()
             result = rpc.RpcRunner.call_jobqueue_update(names, addrs, file_name, data)
             self._CheckRpcResult(result, self._nodes, "Updating %s" % file_name)
         def _RenameFilesUnlocked(self, rename):
           """Renames a file locally and then replicate the change.
           This function will rename a file in the local queue directory
           and then replicate this rename to all the other nodes we have.
           @type rename: list of (old, new)
           @param rename: List containing tuples mapping old to new names
           """
           # Rename them locally
           for old, new in rename:
             utils.RenameFile(old, new, mkdir=True)
           # ... and on all nodes
           names, addrs = self._GetNodeIp()
           result = rpc.RpcRunner.call_jobqueue_rename(names, addrs, rename)
           self._CheckRpcResult(result, self._nodes, "Renaming files (%r)" % rename)
         @staticmethod
         def _FormatJobID(job_id):
           """Convert a job ID to string format.
           Currently this just does C{str(job_id)} after performing some
           checks, but if we want to change the job id format this will
           abstract this change.
           @type job_id: int or long
           @param job_id: the numeric job id
           @rtype: str
           @return: the formatted job id
           """
           if not isinstance(job_id, (int, long)):
             raise errors.ProgrammerError("Job ID '%s' not numeric" % job_id)
           if job_id < 0:
             raise errors.ProgrammerError("Job ID %s is negative" % job_id)
           return str(job_id)
         @classmethod
         def _GetArchiveDirectory(cls, job_id):
           """Returns the archive directory for a job.
           @type job_id: str
           @param job_id: Job identifier
           @rtype: str
           @return: Directory name
           """
           return str(int(job_id) / JOBS_PER_ARCHIVE_DIRECTORY)
         def _NewSerialsUnlocked(self, count):
           """Generates a new job identifier.
           Job identifiers are unique during the lifetime of a cluster.
           @type count: integer
           @param count: how many serials to return
           @rtype: str
           @return: a string representing the job identifier.
           """
           assert count > 0
           # New number
           serial = self._last_serial + count
           # Write to file
           self._UpdateJobQueueFile(constants.JOB_QUEUE_SERIAL_FILE,
                                    "%s\n" % serial, True)
           result = [self._FormatJobID(v)
                     for v in range(self._last_serial, serial + 1)]
           # Keep it only if we were able to write the file
           self._last_serial = serial
           return result
         @staticmethod
         def _GetJobPath(job_id):
           """Returns the job file for a given job id.
           @type job_id: str
           @param job_id: the job identifier
           @rtype: str
           @return: the path to the job file
           """
           return utils.PathJoin(constants.QUEUE_DIR, "job-%s" % job_id)
         @classmethod
         def _GetArchivedJobPath(cls, job_id):
           """Returns the archived job file for a give job id.
           @type job_id: str
           @param job_id: the job identifier
           @rtype: str
           @return: the path to the archived job file
           """
           return utils.PathJoin(constants.JOB_QUEUE_ARCHIVE_DIR,
                                 cls._GetArchiveDirectory(job_id), "job-%s" % job_id)
         def _GetJobIDsUnlocked(self, sort=True):
           """Return all known job IDs.
           The method only looks at disk because it's a requirement that all
           jobs are present on disk (so in the _memcache we don't have any
           extra IDs).
           @type sort: boolean
           @param sort: perform sorting on the returned job ids
           @rtype: list
           @return: the list of job IDs
           """
           jlist = []
           for filename in utils.ListVisibleFiles(constants.QUEUE_DIR):
             m = self._RE_JOB_FILE.match(filename)
             if m:
               jlist.append(m.group(1))
           if sort:
             jlist = utils.NiceSort(jlist)
           return jlist
         def _LoadJobUnlocked(self, job_id):
           """Loads a job from the disk or memory.
           Given a job id, this will return the cached job object if
           existing, or try to load the job from the disk. If loading from
           disk, it will also add the job to the cache.
           @param job_id: the job id
           @rtype: L{_QueuedJob} or None
           @return: either None or the job object
           """
           job = self._memcache.get(job_id, None)
           if job:
             logging.debug("Found job %s in memcache", job_id)
             return job
           try:
             job = self._LoadJobFromDisk(job_id)
             if job is None:
               return job
           except errors.JobFileCorrupted:
             old_path = self._GetJobPath(job_id)
             new_path = self._GetArchivedJobPath(job_id)
             if old_path == new_path:
               # job already archived (future case)
               logging.exception("Can't parse job %s", job_id)
             else:
               # non-archived case
               logging.exception("Can't parse job %s, will archive.", job_id)
               self._RenameFilesUnlocked([(old_path, new_path)])
             return None
           self._memcache[job_id] = job
           logging.debug("Added job %s to the cache", job_id)
           return job
         def _LoadJobFromDisk(self, job_id):
           """Load the given job file from disk.
           Given a job file, read, load and restore it in a _QueuedJob format.
           @type job_id: string
           @param job_id: job identifier
           @rtype: L{_QueuedJob} or None
           @return: either None or the job object
           """
           filepath = self._GetJobPath(job_id)
           logging.debug("Loading job from %s", filepath)
           try:
             raw_data = utils.ReadFile(filepath)
           except EnvironmentError, err:
             if err.errno in (errno.ENOENT, ):
               return None
             raise
           try:
             data = serializer.LoadJson(raw_data)
             job = _QueuedJob.Restore(self, data)
           except Exception, err: # pylint: disable-msg=W0703
             raise errors.JobFileCorrupted(err)
           return job
         def SafeLoadJobFromDisk(self, job_id):
           """Load the given job file from disk.
           Given a job file, read, load and restore it in a _QueuedJob format.
           In case of error reading the job, it gets returned as None, and the
           exception is logged.
           @type job_id: string
           @param job_id: job identifier
           @rtype: L{_QueuedJob} or None
           @return: either None or the job object
           """
           try:
             return self._LoadJobFromDisk(job_id)
           except (errors.JobFileCorrupted, EnvironmentError):
             logging.exception("Can't load/parse job %s", job_id)
             return None
         @staticmethod
         def _IsQueueMarkedDrain():
           """Check if the queue is marked from drain.
           This currently uses the queue drain file, which makes it a
           per-node flag. In the future this can be moved to the config file.
           @rtype: boolean
           @return: True of the job queue is marked for draining
           """
           return os.path.exists(constants.JOB_QUEUE_DRAIN_FILE)
         def _UpdateQueueSizeUnlocked(self):
           """Update the queue size.
           """
           self._queue_size = len(self._GetJobIDsUnlocked(sort=False))
         @locking.ssynchronized(_LOCK)
         @_RequireOpenQueue
         def SetDrainFlag(self, drain_flag):
           """Sets the drain flag for the queue.
           @type drain_flag: boolean
           @param drain_flag: Whether to set or unset the drain flag
           """
           getents = runtime.GetEnts()
           if drain_flag:
             utils.WriteFile(constants.JOB_QUEUE_DRAIN_FILE, data="", close=True,
                             uid=getents.masterd_uid, gid=getents.masterd_gid)
           else:
             utils.RemoveFile(constants.JOB_QUEUE_DRAIN_FILE)
           self._drained = drain_flag
           return True
         @_RequireOpenQueue
         def _SubmitJobUnlocked(self, job_id, ops):
           """Create and store a new job.
           This enters the job into our job queue and also puts it on the new
           queue, in order for it to be picked up by the queue processors.
           @type job_id: job ID
           @param job_id: the job ID for the new job
           @type ops: list
           @param ops: The list of OpCodes that will become the new job.
           @rtype: L{_QueuedJob}
           @return: the job object to be queued
           @raise errors.JobQueueDrainError: if the job queue is marked for draining
           @raise errors.JobQueueFull: if the job queue has too many jobs in it
           @raise errors.GenericError: If an opcode is not valid
           """
           # Ok when sharing the big job queue lock, as the drain file is created when
           # the lock is exclusive.
           if self._drained:
             raise errors.JobQueueDrainError("Job queue is drained, refusing job")
           if self._queue_size >= constants.JOB_QUEUE_SIZE_HARD_LIMIT:
             raise errors.JobQueueFull()
           job = _QueuedJob(self, job_id, ops)
           # Check priority
           for idx, op in enumerate(job.ops):
             if op.priority not in constants.OP_PRIO_SUBMIT_VALID:
               allowed = utils.CommaJoin(constants.OP_PRIO_SUBMIT_VALID)
               raise errors.GenericError("Opcode %s has invalid priority %s, allowed"
                                         " are %s" % (idx, op.priority, allowed))
           # Write to disk
           self.UpdateJobUnlocked(job)
           self._queue_size += 1
           logging.debug("Adding new job %s to the cache", job_id)
           self._memcache[job_id] = job
           return job
         @locking.ssynchronized(_LOCK)
         @_RequireOpenQueue
         def SubmitJob(self, ops):
           """Create and store a new job.
           @see: L{_SubmitJobUnlocked}
           """
           job_id = self._NewSerialsUnlocked(1)[0]
           self._EnqueueJobs([self._SubmitJobUnlocked(job_id, ops)])
           return job_id
         @locking.ssynchronized(_LOCK)
         @_RequireOpenQueue
         def SubmitManyJobs(self, jobs):
           """Create and store multiple jobs.
           @see: L{_SubmitJobUnlocked}
           """
           results = []
           added_jobs = []
           all_job_ids = self._NewSerialsUnlocked(len(jobs))
           for job_id, ops in zip(all_job_ids, jobs):
             try:
               added_jobs.append(self._SubmitJobUnlocked(job_id, ops))
               status = True
               data = job_id
             except errors.GenericError, err:
               data = str(err)
               status = False
             results.append((status, data))
           self._EnqueueJobs(added_jobs)
           return results
         def _EnqueueJobs(self, jobs):
           """Helper function to add jobs to worker pool's queue.
           @type jobs: list
           @param jobs: List of all jobs
           """
           self._wpool.AddManyTasks([(job, ) for job in jobs],
                                    priority=[job.CalcPriority() for job in jobs])
         @_RequireOpenQueue
         def UpdateJobUnlocked(self, job, replicate=True):
           """Update a job's on disk storage.
           After a job has been modified, this function needs to be called in
           order to write the changes to disk and replicate them to the other
           nodes.
           @type job: L{_QueuedJob}
           @param job: the changed job
           @type replicate: boolean
           @param replicate: whether to replicate the change to remote nodes
           """
           filename = self._GetJobPath(job.id)
           data = serializer.DumpJson(job.Serialize(), indent=False)
           logging.debug("Writing job %s to %s", job.id, filename)
           self._UpdateJobQueueFile(filename, data, replicate)
         def WaitForJobChanges(self, job_id, fields, prev_job_info, prev_log_serial,
                               timeout):
           """Waits for changes in a job.
           @type job_id: string
           @param job_id: Job identifier
           @type fields: list of strings
           @param fields: Which fields to check for changes
           @type prev_job_info: list or None
           @param prev_job_info: Last job information returned
           @type prev_log_serial: int
           @param prev_log_serial: Last job message serial number
           @type timeout: float
           @param timeout: maximum time to wait in seconds
           @rtype: tuple (job info, log entries)
           @return: a tuple of the job information as required via
               the fields parameter, and the log entries as a list
               if the job has not changed and the timeout has expired,
               we instead return a special value,
               L{constants.JOB_NOTCHANGED}, which should be interpreted
               as such by the clients
           """
           load_fn = compat.partial(self.SafeLoadJobFromDisk, job_id)
           helper = _WaitForJobChangesHelper()
           return helper(self._GetJobPath(job_id), load_fn,
                         fields, prev_job_info, prev_log_serial, timeout)
         @locking.ssynchronized(_LOCK)
         @_RequireOpenQueue
         def CancelJob(self, job_id):
           """Cancels a job.
           This will only succeed if the job has not started yet.
           @type job_id: string
           @param job_id: job ID of job to be cancelled.
           """
           logging.info("Cancelling job %s", job_id)
           job = self._LoadJobUnlocked(job_id)
           if not job:
             logging.debug("Job %s not found", job_id)
             return (False, "Job %s not found" % job_id)
           (success, msg) = job.Cancel()
           if success:
             self.UpdateJobUnlocked(job)
           return (success, msg)
         @_RequireOpenQueue
         def _ArchiveJobsUnlocked(self, jobs):
           """Archives jobs.
           @type jobs: list of L{_QueuedJob}
           @param jobs: Job objects
           @rtype: int
           @return: Number of archived jobs
           """
           archive_jobs = []
           rename_files = []
           for job in jobs:
             if job.CalcStatus() not in constants.JOBS_FINALIZED:
               logging.debug("Job %s is not yet done", job.id)
               continue
             archive_jobs.append(job)
             old = self._GetJobPath(job.id)
             new = self._GetArchivedJobPath(job.id)
             rename_files.append((old, new))
           # TODO: What if 1..n files fail to rename?
           self._RenameFilesUnlocked(rename_files)
           logging.debug("Successfully archived job(s) %s",
                         utils.CommaJoin(job.id for job in archive_jobs))
           # Since we haven't quite checked, above, if we succeeded or failed renaming
           # the files, we update the cached queue size from the filesystem. When we
           # get around to fix the TODO: above, we can use the number of actually
           # archived jobs to fix this.
           self._UpdateQueueSizeUnlocked()
           return len(archive_jobs)
         @locking.ssynchronized(_LOCK)
         @_RequireOpenQueue
         def ArchiveJob(self, job_id):
           """Archives a job.
           This is just a wrapper over L{_ArchiveJobsUnlocked}.
           @type job_id: string
           @param job_id: Job ID of job to be archived.
           @rtype: bool
           @return: Whether job was archived
           """
           logging.info("Archiving job %s", job_id)
           job = self._LoadJobUnlocked(job_id)
           if not job:
             logging.debug("Job %s not found", job_id)
             return False
           return self._ArchiveJobsUnlocked([job]) == 1
         @locking.ssynchronized(_LOCK)
         @_RequireOpenQueue
         def AutoArchiveJobs(self, age, timeout):
           """Archives all jobs based on age.
           The method will archive all jobs which are older than the age
           parameter. For jobs that don't have an end timestamp, the start
           timestamp will be considered. The special '-1' age will cause
           archival of all jobs (that are not running or queued).
           @type age: int
           @param age: the minimum age in seconds
           """
           logging.info("Archiving jobs with age more than %s seconds", age)
           now = time.time()
           end_time = now + timeout
           archived_count = 0
           last_touched = 0
           all_job_ids = self._GetJobIDsUnlocked()
           pending = []
           for idx, job_id in enumerate(all_job_ids):
             last_touched = idx + 1
             # Not optimal because jobs could be pending
             # TODO: Measure average duration for job archival and take number of
             # pending jobs into account.
             if time.time() > end_time:
               break
             # Returns None if the job failed to load
             job = self._LoadJobUnlocked(job_id)
             if job:
               if job.end_timestamp is None:
                 if job.start_timestamp is None:
                   job_age = job.received_timestamp
                 else:
                   job_age = job.start_timestamp
               else:
                 job_age = job.end_timestamp
               if age == -1 or now - job_age[0] > age:
                 pending.append(job)
                 # Archive 10 jobs at a time
                 if len(pending) >= 10:
                   archived_count += self._ArchiveJobsUnlocked(pending)
                   pending = []
           if pending:
             archived_count += self._ArchiveJobsUnlocked(pending)
           return (archived_count, len(all_job_ids) - last_touched)
         def QueryJobs(self, job_ids, fields):
           """Returns a list of jobs in queue.
           @type job_ids: list
           @param job_ids: sequence of job identifiers or None for all
           @type fields: list
           @param fields: names of fields to return
           @rtype: list
           @return: list one element per job, each element being list with
               the requested fields
           """
           jobs = []
           list_all = False
           if not job_ids:
             # Since files are added to/removed from the queue atomically, there's no
             # risk of getting the job ids in an inconsistent state.
             job_ids = self._GetJobIDsUnlocked()
             list_all = True
           for job_id in job_ids:
             job = self.SafeLoadJobFromDisk(job_id)
             if job is not None:
               jobs.append(job.GetInfo(fields))
             elif not list_all:
               jobs.append(None)
           return jobs
         @locking.ssynchronized(_LOCK)
         @_RequireOpenQueue
         def Shutdown(self):
           """Stops the job queue.
           This shutdowns all the worker threads an closes the queue.
           """
           self._wpool.TerminateWorkers()
           self._queue_filelock.Close()
           self._queue_filelock = None

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